This application relates to a unique assembly for detecting oil contamination in a vehicular pneumatic brake system.
Heavy vehicles, such as trucks and tractor-trailers, typically use a pneumatic brake system. Pneumatic brake systems, sometimes referred to as compressed air brake systems, use air pressure to actuate the brakes of the heavy vehicle. Typically, pneumatic brake systems include an air compressor and an air dryer. The air compressor includes a cylinder, a piston which reciprocates within the cylinder, and a piston seal disposed between the outer circumference of the piston and the inner circumference of the cylinder. The reciprocating movement of the piston is used to compress or pressurize the brake system air supply. The air dryer includes a canister filled with desiccant to remove moisture and other contaminants from the air supply. Periodically, the canister is purged to remove the moisture absorbed by the desiccant.
Pneumatic brake systems often experience an oil contamination condition, commonly referred to as "blow-by". This type of contamination occurs when lubricating oil located on one side of the air compressor piston is blown by the piston seal into the brake system air supply located on the opposing side of the piston. As the contaminated air is moved through the air dryer, the oil is absorbed by the desiccant. Unlike moisture, oil absorbed by the desiccant cannot be purged out of the air dryer. Over time, the absorption and retention of an increasing amount of oil prevents the desiccant from absorbing additional moisture, thereby allowing some moisture to pass through the air dryer into other portions of the brake system. This non-absorbed moisture can freeze inside the brake system during cold temperature conditions and damage many brake system components.
To avoid brake system damage caused by oil contamination, the air dryer must be periodically serviced by replacing the desiccant canister. Determining when to service the air dryer for excessive oil contamination is a difficult task. Accordingly, it would be desirable to provide an oil contamination detection assembly for detecting when service of the air dryer for oil contamination is necessary.